Migrate CI to SciML centralized reusable workflows

[ChrisRackauckas-Claude]

Please ignore until reviewed by @ChrisRackauckas.

Normalizes CI to the SciML centralized reusable workflows (SciML/.github/.github/workflows/*.yml@v1), matching the Sundials.jl standard set.

Workflows

Converted to centralized callers (@v1):

• CI.yml -> Tests.yml — tests.yml@v1. Preserves the exact name: CI, the push/pull_request triggers with paths-ignore: docs/**, the concurrency block, and the version matrix ['1', 'lts', 'pre']. Coverage stays on (the original collected codecov).
• Downgrade.yml — downgrade.yml@v1. Preserves julia-version: 1.10, skip: Pkg,TOML, and the disabling if: false (lower compat bounds don't resolve on Julia 1.10).
• SpellCheck.yml — spellcheck.yml@v1 (was crate-ci/typos, pull_request trigger preserved).

Added (new standard checks):

• FormatCheck.yml — runic.yml@v1. The repo did not previously run Runic.

Removed:

• CompatHelper.yml — replaced by Dependabot's Julia ecosystem updates.

Unchanged:

• TagBot.yml.

Runic formatting

The repo was previously unformatted (no Runic check). Runic 1.7.0 was run in-place over all 200 parseable tracked .jl files and committed; they now pass runic --check.

Heads-up — the Runic check will be RED. 11 legacy .jl files contain pre-1.0 Julia syntax that Runic (JuliaSyntax) cannot parse, so the centralized check (which runs over all git-tracked .jl files) will fail on them:

• examples/benchmarking/updatetoplist.jl
• spikes/benchmarking.jl, spikes/comparing_covariate_selection_schemes.jl, spikes/covar_matrix_adaptation_es.jl, spikes/diversity_guided_mutation.jl, spikes/experiments/gss_initial.jl, spikes/lasso_active_factor_prediction.jl, spikes/parameter_study.jl, spikes/subset_tournament_cmsa_es/subset_tournament_cmsa_es.jl, spikes/test_acd.jl, spikes/test_acd_acf.jl

These are experimental/exploratory files (already excluded from the typos check) using deprecated syntax such as 2.^[2,6] and op = cond ? < : >. Fixing or removing them is a content change beyond CI normalization and is left to the maintainer's discretion. Runic has no exclude mechanism, so the check stays red until these are addressed.

Dependabot

• Kept the existing github-actions block (weekly).
• Added a julia block (directory: "/", daily, group all-julia-packages: ["*"]) to preserve compat automation after CompatHelper removal. Only the repo root has a Project.toml (no docs/Project.toml or test/Project.toml).

Spellcheck / typos

typos runs clean locally (exit 0); the existing .typos.toml covers the false positives. No prose was changed.

Branch protection

Check names change (e.g. test -> Tests, plus new Runic Format Check). Branch-protection required-status-checks will need updating.

🤖 Generated with Claude Code